Light input/output device

An optical input/output device comprising:

• an input port and an output port configured to input and output signal light, respectively;
• a phase modulator element including a plurality of pixels arranged in a matrix in a plane, a pattern generator unit configured to generate a phase pattern which is a combination of phase values set for each pixel to provide optical coupling to a desired port out of the input port and the output port, a control unit configured to convert the phase pattern into a driving signal for each pixel, and a driver unit configured to drive the pixel according to the driving signal, the phase modulator element being configured to change an optical phase of the signal light entering each pixel, by the driver unit applying the driving signal corresponding to the phase pattern;
• and
• an optical element configured to convert a direction of exit of the signal light so as to irradiate each pixel in the plane of the phase modulator element with the signal light exiting from the input port to a space,
• wherein the pattern generator unit includes superimposing means for superimposing a periodic phase pattern having a predetermined period in at least one direction in the plane of the phase modulator element which the signal light enters, and means for controlling an amplitude of the periodic phase pattern, and
• the signal light is diffracted to a position according to the period and pattern shape of the periodic phase pattern superimposed on the phase pattern capable of providing desired optical coupling between the input port and the output port, so that light intensity of the signal light is dispersed.